MM-13664 Cache external link metadata when populating post metadata (#10128)

* MM-13664 Added LinkMetadata types

* MM-13664 Use LinkMetadata when populating post metadata

* Fix unused import

* Fix index name on SQLite

* Finish adding unit tests

* Address feedback

* Increase max length of URL column to 2048 characters

store/sqlstore/link_metadata_store.go

@@ -0,0 +1,88 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package sqlstore
+
+import (
+	"database/sql"
+	"net/http"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/store"
+)
+
+type SqlLinkMetadataStore struct {
+	SqlStore
+}
+
+func NewSqlLinkMetadataStore(sqlStore SqlStore) store.LinkMetadataStore {
+	s := &SqlLinkMetadataStore{sqlStore}
+
+	for _, db := range sqlStore.GetAllConns() {
+		table := db.AddTableWithName(model.LinkMetadata{}, "LinkMetadata").SetKeys(false, "Hash")
+		table.ColMap("URL").SetMaxSize(2048)
+		table.ColMap("Type").SetMaxSize(16)
+		table.ColMap("Data").SetMaxSize(4096)
+	}
+
+	return s
+}
+
+func (s SqlLinkMetadataStore) CreateIndexesIfNotExists() {
+	if s.DriverName() == model.DATABASE_DRIVER_MYSQL {
+		s.CreateCompositeIndexIfNotExists("idx_link_metadata_url_timestamp", "LinkMetadata", []string{"URL(512)", "Timestamp"})
+	} else {
+		s.CreateCompositeIndexIfNotExists("idx_link_metadata_url_timestamp", "LinkMetadata", []string{"URL", "Timestamp"})
+	}
+}
+
+func (s SqlLinkMetadataStore) Save(metadata *model.LinkMetadata) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		if result.Err = metadata.IsValid(); result.Err != nil {
+			return
+		}
+
+		metadata.PreSave()
+
+		err := s.GetMaster().Insert(metadata)
+		if err != nil {
+			result.Err = model.NewAppError("SqlLinkMetadataStore.Save", "store.sql_link_metadata.save.app_error", nil, "url="+metadata.URL+", "+err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		result.Data = metadata
+	})
+}
+
+func (s SqlLinkMetadataStore) Get(url string, timestamp int64) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		var metadata *model.LinkMetadata
+
+		err := s.GetReplica().SelectOne(&metadata,
+			`SELECT
+				*
+			FROM
+				LinkMetadata
+			WHERE
+				URL = :URL
+				AND Timestamp = :Timestamp`, map[string]interface{}{"URL": url, "Timestamp": timestamp})
+		if err != nil {
+			result.Err = model.NewAppError("SqlLinkMetadataStore.Get", "store.sql_link_metadata.get.app_error", nil, "url="+url+", "+err.Error(), http.StatusInternalServerError)
+
+			if err == sql.ErrNoRows {
+				result.Err.StatusCode = http.StatusNotFound
+			}
+
+			return
+		}
+
+		err = metadata.DeserializeDataToConcreteType()
+		if err != nil {
+			result.Err = model.NewAppError("SqlLinkMetadataStore.Get", "store.sql_link_metadata.get.app_error", nil, "url="+url+", "+err.Error(), http.StatusInternalServerError)
+
+			return
+		}
+
+		result.Data = metadata
+	})
+}